wrt-ls is a provisional interface to the tools in WRT::EntryStore.  It
should do more, but work is needed that I'm not going to put in before
releasing v5.0.0.

This seems like a good point to call things stable for this major release.
I have a bunch of ideas that I'd like to implement for a v6, which might
well break the API and underlying data structures.

This is all pretty academic since no one else actually uses this thing.